//html5 图片上传类
function UploadPic() { 
    this.sw = 0; 
    this.sh = 0; 
    this.tw = 0; 
    this.th = 0; 
    this.scale = 0; 
    this.maxWidth = 0; 
    this.maxHeight = 0; 
    this.maxSize = 0; 
    this.fileSize = 0; 
    this.fileDate = null; 
    this.fileType = ''; 
    this.fileName = ''; 
    this.input = null; 
    this.canvas = null; 
    this.mime = {}; 
    this.type = ''; 
    this.callback = function () {}; 
    this.loading = function () {};
}

UploadPic.prototype.init = function (options) {
    this.maxWidth = options.maxWidth || 800;
    this.maxHeight = options.maxHeight || 600;
    this.maxSize = options.maxSize || 3 * 1024 * 1024;
    this.input = options.input;
    this.mime = {'png': 'image/png', 'jpg': 'image/jpeg', 'jpeg': 'image/jpeg', 'bmp': 'image/bmp'};
    this.callback = options.callback || function () {
    };
    this.loading = options.loading || function () {
    };
    this._addEvent();
};

/** 
 * @description 绑定事件 
 * @param {Object} elm 元素 
 * @param {Function} fn 绑定函数 
 */
UploadPic.prototype._addEvent = function () {
    var _this = this;

    function tmpSelectFile(ev) {
        _this._handelSelectFile(ev);
    }
    this.input.addEventListener('change', tmpSelectFile, false);
};

/** 
 * @description 绑定事件 
 * @param {Object} elm 元素 
 * @param {Function} fn 绑定函数 
 */
UploadPic.prototype._handelSelectFile = function (ev) {
    var file = ev.target.files[0];
    this.type = file.type

// 如果没有文件类型，则通过后缀名判断（解决微信及360浏览器无法获取图片类型问题） 
    if (!this.type) {
        this.type = this.mime[file.name.match(/\.([^\.]+)$/i)[1]];
    }

    if (!/image.(png|jpg|jpeg|bmp)/.test(this.type)) {
        alert('选择的文件类型不是图片');
        return;
    }

    if (file.size > this.maxSize) {
        alert('选择文件大于' + this.maxSize / 1024 / 1024 + 'M，请重新选择');
        return;
    }

    this.fileName = file.name;
    this.fileSize = file.size;
    this.fileType = this.type;
    this.fileDate = file.lastModifiedDate;

    this._readImage(file);
};

/** 
 * @description 读取图片文件 
 * @param {Object} image 图片文件 
 */
UploadPic.prototype._readImage = function (file) {
    var _this = this;

    function tmpCreateImage(uri) {
        _this._createImage(uri);
    }
    this.loading();
    this._getURI(file, tmpCreateImage);
};

/** 
 * @description 通过文件获得URI 
 * @param {Object} file 文件 
 * @param {Function} callback 回调函数，返回文件对应URI 
 * return {Bool} 返回false 
 */
UploadPic.prototype._getURI = function (file, callback) {
    var reader = new FileReader();
    var _this = this;

    function tmpLoad() {
        // 头不带图片格式，需填写格式 
        var re = /^data:base64,/;
        var ret = this.result + '';
        if (re.test(ret))
            ret = ret.replace(re, 'data:' + _this.mime[_this.fileType] + ';base64,');
        callback && callback(ret);
    }

    reader.onload = tmpLoad;
    reader.readAsDataURL(file);

    return false;
};
/** 
 * @description 创建图片 
 * @param {Object} image 图片文件 
 */
UploadPic.prototype._createImage = function (uri) {
    var img = new Image();
    var _this = this;

    function tmpLoad() {
        _this._drawImage(this);
    }

    img.onload = tmpLoad;

    img.src = uri;
};
/** 
 * @description 创建Canvas将图片画至其中，并获得压缩后的文件 
 * @param {Object} img 图片文件 
 * @param {Number} width 图片最大宽度 
 * @param {Number} height 图片最大高度 
 * @param {Function} callback 回调函数，参数为图片base64编码 
 * return {Object} 返回压缩后的图片 
 */
UploadPic.prototype._drawImage = function (img, callback) {
    this.sw = img.width;
    this.sh = img.height;
    this.tw = img.width;
    this.th = img.height;

    this.scale = (this.tw / this.th).toFixed(2);

    if (this.sw > this.maxWidth) {
        this.sw = this.maxWidth;
        this.sh = Math.round(this.sw / this.scale);
    }
    if (this.sh > this.maxHeight) {
        this.sh = this.maxHeight;
        this.sw = Math.round(this.sh * this.scale);
    }
    this.canvas = document.createElement('canvas');
    var ctx = this.canvas.getContext('2d');
    this.canvas.width = this.sw;
    this.canvas.height = this.sh;
    ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, this.sw, this.sh);
    this.callback(this.canvas.toDataURL(this.type));
    ctx.clearRect(0, 0, this.tw, this.th);
    this.canvas.width = 0;
    this.canvas.height = 0;
    this.canvas = null;
};